X-ray equipment may be considered as being of the general category or of the microfocus category. In the general category, the electron beam bombarding the X-ray emitting target is not subjected to substantial focusing, and the resulting X-ray beam spot size is on the order of 0.2 mm to 5.0 mm; whereas, in the microfocus category, the electron beam is focused in a manner to achieve a quite small X-ray spot size, on the order of 10 to 200 microns. Obviously, much greater detail or resolution of viewing is achieveable with the smaller focal spot size of the microfocus equipment as the X rays essentially emanate from a point source. Up until this time, microfocus systems which provided such detail simply did not provide sufficient X-ray output to enable real time viewing, as, for example, adequate for employment with real time image display systems as opposed to the exposure of film.
In addition to the general field of microfocus X-ray systems as dealt with by this invention, its application to real time stereofluoroscopy and tomofluoroscopy appears to be substantial. As the name implies, stereofluoroscopy provides a three-dimensional X-ray image containing depth information, while tomography provides the ability to image a single planar layer of an object. While film-type stereoradiography and tomography are well established, especially in medical radiology, real time versions of these important techniques have not been very successful. Some investigators have looked into the practicality of stereofluoroscopy employing two conventional X-ray sources. A serious limitation with this is that the X-ray sources, or tubeheads, be separated by a distance equal to approximately 10% of the tubehead-to-image receptor distance in order to produce the 6.degree. stereo viewing angle the human viewing eye-brain combination requires. Mechanical considerations make this difficult to achieve inasmuch as X-ray tubeheads are bulky, yet they must be precisely positioned, posing both space problems and cost. Further, the two X-ray tubeheads must be alternately switched on and off at TV frame rates if a TV viewing system is to be employed; otherwise, two complete imaging systems must be used, a very complicated, expensive arrangement. In any event, real time stereofluoroscopy has not become a significant reality.
Similarly, with respect to real time tomosynthesis, while film-type tomographic X-ray systems are to be found in many hospitals, little known progress has been made in the direction of achieving real time X-ray tomosynthesis. The problem here is largely because of the mechanical difficulty of achieving a close mechanical displacement of separate X-ray tubeheads and their positioning about a central pivot point lying in the plane of interest of an object.
Accordingly, and in light of the state of real time X-ray systems as described, it is an object of the present invention to provide a new and improved microfocus X-ray system and one which is suitable for and readily enables both real time stereofluoroscopy and tomosynthesis.